Conventionally, when a user searches for a desired image scene from recorded video data in a video recording apparatus for encoding and recording video data, the user visually searches for a target image scene by using special reproduction such as fast-forwarding or fast-reversing. This requires a lot of time and work of the user.
In order to solve such problem, methods of searching for a scene transition (hereinafter referred to as a “scene change”) in a video have been proposed (e.g., see Patent Documents 1 and 2). Patent Document 1 discloses a method, in which a video signal processing apparatus at a stage previous to an encoder for encode processing calculates an absolute value of a difference between histograms of two pictures adjacent to each other in time and determines that a scene change takes place when the calculated absolute value exceeds a predetermined threshold value. Further, Patent Document 2 discloses a method, in which the video data that have already been stored in a storage medium of an HDD are read to extract a scene change.
Further, television broadcasts can be classified into a “program main part broadcast” and a “commercial message broadcast” on the basis of their contents. In the case of a movie program, the program main part broadcast is a broadcast portion based on the video audio data of a movie content itself. On the other hand, the commercial message broadcast is a broadcast portion based on the video audio data supplied by a client such as an advertiser, an advertisement agent, or the like, who exchanges contracts with a broadcasting company, and is broadcasted during time between the program main part broadcasts. Furthermore, the commercial message broadcast includes a broadcast portion which is broadcasted by a broadcasting company in order to advertise and publicize its own company. In the present application, the “program main part broadcast” is also referred to as a “program main part”, and the “commercial message broadcast” is also referred to as a “CM broadcast”. The relationship between contents of the program main part and the CM broadcast tends to be slight. Therefore, a viewer who wants to concentrate his energies on watching the program main parts has a desire that an apparatus effectively removes the CM broadcasts when the television broadcast is recorded or an apparatus skips the CM broadcasts when the television broadcast is viewed.
A conventional video audio recording apparatus detects an audio scheme of a television broadcast, and discriminates between a program main part and a CM broadcast based on the detected audio scheme. An audio scheme of the program main part tends to be a monophonic sound or a bilingual sound (e.g., Japanese and English in a foreign film), while an audio scheme of the CM broadcast generally tends to be a stereophonic sound. Using such difference, the apparatus determines that a period of time when a stereophonic sound is detected is a CM broadcast period, does not record (i.e., removes) video data of a CM broadcast period during video recording, and avoids watching (i.e., skips) a CM broadcast during video viewing.
The above-mentioned conventional CM detection method is useless when the audio scheme of the program main part is the same as the audio scheme of the CM broadcast, i.e., a stereophonic sound. To resolve this problem, there is provided with a proposal of detecting a frame picture of a whole black frame referred to as a “black frame” that is inserted in a boundary between a program main part and a CM broadcast, thereby identifying a CM broadcast period (e.g., see Patent Document 3). Further, there is provided with a proposal of detecting a silence period which appears in a boundary between a program main part and a CM broadcast, thereby identifying a CM broadcast period based on an interval between occurrences of the detected silence periods (e.g., see Patent Document 4). Furthermore, there is provided with a proposal of extracting a CM broadcast using an occurrence frequency of a scene change in a video (see Patent Document 5). Moreover, there is provided with a proposal of a user interface used to avoid watching (i.e., skip) a fixed period of time such as 15 seconds by user's button operation during video viewing.    Patent Document 1 is Japanese Patent Application Kokai (Laid-Open) Publication No. 2004-282318 (page 7, FIG. 2);    Patent Document 2 is Japanese Patent Application Kokai (Laid-Open) Publication No. 2002-064823 (page 5, FIG. 1);    Patent Document 3 is Japanese Patent Kohyo (Japanese Translation of International Patent Application) H8-507633 (pages 12-15, FIG. 1);    Patent Document 4 is Japanese Patent Application Kokai (Laid-Open) Publication No. 2003-47031 (pages 5-8, FIG. 1); and    Patent Document 5 is Japanese Patent Application Kokai (Laid-Open) Publication No. 2000-165796 (page 7, FIG. 14).